Re: FYI: coreutils/gnulib-tests to run in parallel

[Ralf Wildenhues]

* Jim Meyering wrote on Fri, Jun 13, 2008 at 10:17:36AM CEST:
> Ralf Wildenhues <address@hidden> wrote:
> 
> > Just ordering the build of some huge objects in GCC allowed to shave 30%
> > build time off a parallel build:
> 
> Yes, I did the same with coreutils/tests, and it made a big difference,
> since there were some long-running tests near the end of the initial list.
> Here it was the first thing I tried, once parallelized.  However, in
> this case it gave less than 1 second decrease.  No big surprise, though,
> since even removing the top 4-5 longest-running tests shaves only ~8
> seconds off the total (~11s) run time, now that they're run in parallel.

IIRC most of the coreutils tests are pretty I/O bound.  Running them in
parallel won't help much, with all of them competing for the same kernel
resp. disk resources.  I guess the proposed parallel Autotest patches
are thus limited, too.  I found testing them on tmpfs (/dev/shm) to show
much more favorable speedup than disk or NFS.  You probably may want to
ensure to have a recent kernel, too (although I have no idea whether
there were significant improvements in in-kernel parallelism recently).

Cheers,
Ralf